There goes two other questions :
1) My tiefling rogue just attained level 2 so I decided to dual him to an enchanter. I was quite surprised when I was afford to chosse a feat !!! My total level is 2, so why did I get this new feat ?

2) Still talking of the same character : I have read in the manual that, for multiclassed characters, a skill is a class skill as long as it is a class skill for one of the two classes the character belongs to. However, when distributing skill points, the "rogue class skills" where treated as "cross class skills" for my rogue 1/enchanter 1 character. Is this a bug ?

Well well well, all this is very confusing ...

Still talking of the same character : I have read in the manual that, for multiclassed characters, a skill is a class skill as long as it is a class skill for one of the two classes the character belongs to. However, when distributing skill points, the "rogue class skills" where treated as "cross class skills" for my rogue 1/enchanter 1 character. Is this a bug ? I think it's only a class skill if you are leveling your character up in that class.

Yes, it seems so, although the manual states something different...Too bad ! I have been planning the developement of my caracter for hours using false informations :-(